Efficient generation of radio coverage map of access points in an indoor environment

ABSTRACT

A method for generating a radio coverage map. A two-dimensional radio coverage map located between a first physical level and a second physical level is generated. The access point is located above the second physical level. The two-dimensional radio coverage map is located at a distance from the access point and comprises a plurality of map points, where the map points have a predicted received signal strength value. A projection window is determined. A projected area on the two-dimensional radio coverage map is determined by computing a geometrical projection from the access point through the projection window onto the two-dimensional radio coverage map. A plurality of first points in a first area on the two-dimensional radio coverage map is identified. The first area is outside the projected area. The predicted received signal strength value of each of the first points is reduced by a value equal to the signal attenuation caused by the second physical level.

REFERENCE TO CO-PENDING APPLICATIONS FOR PATENT

The present application for patent is related to the followingco-pending U.S. patent application Ser. No. 13/748,007:

-   -   “Fast Generation of Radio Coverage Map of Access Points in an        Indoor Environment” by Do et al., filed concurrently herewith,        assigned to the assignee hereof, and expressly incorporated by        reference herein.

FIELD OF DISCLOSURE

The presently disclosed embodiments are directed to the field ofgenerating radio coverage maps of access points in an indoorenvironment.

BACKGROUND

A radio coverage map of an access point is a map of the signal strengthof a signal transmitted by the access point as received at variouslocations on the map. Radio coverage maps of access points located in abuilding are important in indoor positioning. Radio coverage maps ofaccess points located in the building are provided to a mobile stationto assist the mobile station in determining its position. Using theradio coverage maps, the mobile station determines which access pointsto scan. The mobile station scans these access points and measuresreceived signal strength indicator (RSSI) values from signalstransmitted by these access points. The radio coverage map is alsocommonly called an RSSI heatmap. The radio coverage map is usually athree-dimensional radio coverage map. The radio coverage map istypically generated in advance by a server. Traditionally, the radiocoverage map is generated by using the well-known dominant path model orray tracing model.

Buildings such as malls and airports often have partial ceilings. Inother words, two or more physical levels (i.e., floors or ceilings) ofsuch building share the same top ceiling. If the partial ceilings areconsidered in the traditional process of generating the radio coveragemaps of the access points located in such building (for example, byusing the dominant path model or ray tracing model), this traditionalprocess will require a very large amount of time and processing power.Thus, using the traditional process, it is not possible to generatequickly a radio coverage map of an access point located in suchbuilding, and it is not feasible for a mobile station, with its limitedprocessing power, to generate a radio coverage map by itself.

SUMMARY

Exemplary embodiments of the invention are directed to systems andmethod for efficiently generating a radio coverage map of an accesspoint in an indoor environment.

A method for generating a radio coverage map for an access point in awireless environment comprising a plurality of physical levels isdisclosed. The plurality of physical levels includes a first physicallevel and a second physical level located above the first physicallevel. The access point is located above the second physical level. Atwo-dimensional radio coverage map located between the first physicallevel and the second physical level is generated without taking intoaccount a signal attenuation caused by the second physical level. Thetwo-dimensional radio coverage map is located at a target distance fromthe access point and comprises a plurality of map points. Each of themap points has a predicted received signal strength value. A projectionwindow located at a same vertical level as the second physical level isdetermined. A projected area on the two-dimensional radio coverage mapis determined by computing a geometrical projection from the accesspoint through the projection window onto the two-dimensional radiocoverage map. A plurality of first points in a first area on thetwo-dimensional radio coverage map is identified. The first area isoutside the projected area. Each of the first points has a predictedreceived signal strength value. The predicted received signal strengthvalue of each of the first points is reduced by a value equal to thesignal attenuation caused by the second physical level.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofembodiments of the invention and are provided solely for illustration ofthe embodiments and not limitation thereof.

FIG. 1 is a diagram illustrating a system 100 in which one embodiment ofthe invention may be practiced.

FIG. 2 is a diagram illustrating a system 200 in which one embodiment ofthe invention may be practiced.

FIG. 3 is a diagram illustrating a system 300 in which one embodiment ofthe invention may be practiced.

FIG. 4 is a diagram illustrating a wireless environment 400 in whichembodiments of the invention may be practiced.

FIG. 5 is a diagram illustrating an embodiment of the invention where atwo-dimensional radio coverage map 440 is generated from a first radiocoverage map 550.

FIG. 6 is a flowchart illustrating a process of generating a radiocoverage map for an access point in a wireless environment according toone embodiment.

FIG. 7 is a flowchart illustrating an embodiment of process 610 shown inFIG. 6.

FIG. 8 is a flowchart illustrating a process of determiningapproximately whether the access point is radio visible from the firstphysical level in a multi-level wireless environment.

FIG. 9 is a flowchart illustrating a process of generating atwo-dimensional radio coverage map for an access point in a wirelessenvironment according to one embodiment.

FIG. 10 is a diagram illustrating an apparatus according to oneembodiment.

DETAILED DESCRIPTION

Aspects of the invention are disclosed in the following description andrelated drawings directed to specific embodiments of the invention.Alternate embodiments may be devised without departing from the scope ofthe invention. Additionally, well-known elements of the invention willnot be described in detail or will be omitted so as not to obscure therelevant details of the invention.

One disclosed feature of the embodiments may be described as a processwhich is usually depicted as a flowchart, a flow diagram, a structurediagram, or a block diagram. Although a flowchart may describe theoperations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be re-arranged. A process is terminated when itsoperations are completed. A process may correspond to a method, aprogram, a procedure, etc. One embodiment may be described by aschematic drawing depicting a physical structure. It is understood thatthe schematic drawing illustrates the basic concept and may not bescaled or depict the structure in exact proportions.

Embodiments of the invention are directed to apparatus and method forefficient generation of radio coverage map of an access point in anindoor environment. The technique provides a simplified process ofgenerating a radio coverage map. The simplified process does not requiremuch of processing power, thus can be performed by a mobile station.Employing the simplified process, either a location assistant server ora mobile station can quickly generate a radio coverage map for an accesspoint. This is of particular benefit for a mobile station, since themobile station can quickly determine which access points are most likelyto be radio visible from the current coarse position of the mobilestation. The mobile station can then focus on these most likely to beradio visible access points for scanning and measurement. An accesspoint is radio visible to the mobile station if the signal strength of asignal transmitted by the access point as received at the current coarseposition of the mobile station is sufficient for communication; in otherwords, the signal strength is above a predetermined minimum threshold.

FIG. 1 is a diagram illustrating a system 100 in which one embodiment ofthe invention may be practiced. The system 100 includes an access pointmanagement server 110, an access point network 120, a plurality ofaccess points 130, a location assistant server 140, and a plurality ofmobile stations 150. The term “venue” is used herein to designate thelocal environment. The access point management server 110 receivesinformation 102 from a venue operator or from information technologypersonnel. The information 102 includes map information of the venue,and information related to the access points located in the venue. Themap information of the venue includes information regarding a structurallayout of the wireless environment, and optionally includes informationregarding material types of the plurality of physical levels (that is,ceilings, floors) in the venue. The information related to the accesspoints located in the venue includes location information of the accesspoints. The access point management server 110 uses the access pointnetwork 120 to communicate with the access points 130. The access pointmanagement server 110 provides information 112 to the location assistantserver 140. The information 112 includes the map information of thevenue, and the information related to the access points located in thevenue. Based on the received information 112, the location assistantserver 140 generates radio coverage maps of the access points located inthe venue. The location assistant server 140 receives requests forassistance from the mobile stations 150 and provides the radio coveragemaps to the mobile stations 150. Embodiments of the invention may bepracticed by the location assistant server 140.

FIG. 2 is a diagram illustrating a system 200 in which one embodiment ofthe invention may be practiced. The system 200 includes a locationassistant server 240 and a plurality of mobile stations 250. Thelocation assistant server 240 receives information 212 directly from avenue operator and/or a public data contributor having access to mapinformation of the venue and information related to the access pointslocated in the venue. The information 212 includes map information ofthe venue, and information related to the access points located in thevenue. The map information of the venue includes information regarding astructural layout of the wireless environment, and optionally includesinformation regarding material types of the plurality of physical levels(that is, ceilings, floors) in the venue. The information related to theaccess points located in the venue includes location information of theaccess points. Based on the received information 212, the locationassistant server 240 generates radio coverage maps of the access pointslocated in the venue. The location assistant server 240 receivesrequests for assistance from the mobile stations 250 and provides theradio coverage maps to the mobile stations 250. Embodiments of theinvention may be practiced by the location assistant server 240.

FIG. 3 is a diagram illustrating a system 300 in which one embodiment ofthe invention may be practiced. The system 300 includes a Web server340, the Internet or intranet 345, and a plurality of mobile stations350. The Web server 340 receives information 312 from a venue operator.The information 312 includes map information of the venue, andinformation related to the access points located in the venue. The mapinformation of the venue includes information regarding a structurallayout of the wireless environment, and optionally includes informationregarding material types of the plurality of physical levels (that is,ceilings, floors) in the venue. The information related to the accesspoints located in the venue includes location information of the accesspoints. The information 312 is saved at the Web server 340 and isaccessible via a Uniform Resource Locator (URL). The mobile stations 350may obtain this URL through known mobile applications. The mobilestations 350 may also obtain this URL by searching for beacons locatedin the venue. The beacons may be radio beacons (such as WiFi accesspoint, Bluetooth access point) or visual beacons (such as Quick Responsecode, other types of matrix codes, and bar codes). Providing this URL tothe Internet/Intranet 345, the mobile stations 350 accesses andretrieves the information 312 stored at the Web server 340. Based on theretrieved information 312, the mobile stations 350 generate radiocoverage maps of the access points located in the venue. Embodiments ofthe invention may be practiced by each of the mobile stations 350.

FIG. 4 is a diagram illustrating a wireless environment 400 in whichembodiments of the invention may be practiced. The wireless environment400 comprises a first physical level 410 and a second physical level 420located above the first physical level 410. The wireless environment 400includes an access point 430 located above the second physical level 420at a distance 422 from the second physical level 420.

A two-dimensional radio coverage map 440 located between the firstphysical level 410 and the second physical level 420 is generated byembodiments of the invention. The two-dimensional radio coverage map 440is located at a target distance 442 from the access point 430, and at adistance 412 from the first physical level 410. The distance 412 iscommonly referred to as the prediction height and ranges from 1 meter to1.5 meters. This prediction height corresponds to a typical distance ofa transceiver of a mobile station from the first physical level 410. Thetwo-dimensional radio coverage map 440 comprises a plurality of mappoints. Each of the map points has a predicted received signal strengthvalue which representing a predicted received signal strength of asignal transmitted by the access point 430. The two-dimensional radiocoverage map 440 comprises a projected area 444 and a first area 446.The first area comprises the map points that are located outside of theprojected area 444. The two-dimensional radio coverage map 440 mayoptionally include a second area 448 which is adjacent to the boundaryof the projected area 444, and comprises transition points.

A projection window 424 is located at a same vertical level as thesecond physical level 420. The projection window may be an open space.The projection window 424 may also be an area having a specific materialtype which causes a specific attenuation to a received signal strengthof a signal transmitted by the access point 430 and passing through theprojection window 424. For example, the specific material type may bewood, or metal, or concrete, etc.

The projected area 444 on the two-dimensional radio coverage map isgenerated by computing a geometrical projection from the access point430 through the projection window 424 onto the two-dimensional radiocoverage map 440.

FIG. 5 is a diagram illustrating an embodiment 500 of the inventionwhere the two-dimensional radio coverage map 440 is generated from afirst radio coverage map 550. The wireless environment comprises thefirst physical level 410 and the second physical level 420, as describedpreviously with respect to FIG. 4.

Referring to FIG. 5, a first two-dimensional radio coverage map 550 forthe access point 430 is generated. In a wireless environment thatincludes more than two physical levels, the first two-dimensional radiocoverage map is preferably at a prediction height above the physicallevel that is closest to the access point. The first two-dimensionalradio coverage map 550 is located at a distance 552 from the accesspoint 430, and at a distance 554 (i.e., prediction height) from thesecond physical level 420. The first two-dimensional radio coverage map550 comprises a plurality of original points. Each of the originalpoints has a predicted value representing a predicted received signalstrength of a signal transmitted by the access point 430.

The target distance 442 is selected to place the two-dimensional radiocoverage map 440 at the target distance 442 from the access point 430.Coordinates of the map points of the two-dimensional radio coverage map440 are generated from coordinates of corresponding original points ofthe first two-dimensional radio coverage map 550. A ratio of the targetdistance 442 to the first distance 552 is used to magnify thecoordinates of an original point of the first two-dimensional radiocoverage map 550 to obtain the coordinates of the corresponding mappoint of the two-dimensional radio coverage map 440. In other words,coordinates of the map points of the two-dimensional radio coverage map440 are generated by magnifying the first radio coverage map 550 using aratio of the target distance 442 to the first distance 552. An offsetvalue representing an attenuation due to the target distance 442 beingdifferent than the first distance 552 is computed. For each of the mappoints of the two-dimensional radio coverage map 440, a predictedreceived signal strength value is generated by adding the offset valueto the predicted value of the corresponding one of the original pointsof the first two-dimensional radio coverage map 550.

FIG. 6 is a flowchart illustrating a process 600 of generating a radiocoverage map for an access point in a wireless environment according toone embodiment. The wireless environment comprises a plurality ofphysical levels including a first physical level and a second physicallevel located above the first physical level.

Referring to FIG. 6 and FIG. 4, upon START, the process 600 generates atwo-dimensional radio coverage map 440 located between the firstphysical level 410 and the second physical level 420 without taking intoaccount a signal attenuation caused by the second physical level 420(Block 610). The access point 430 is located above the second physicallevel 420. The two-dimensional radio coverage map 440 is located at atarget distance 442 from the access point 430 and comprises a pluralityof map points. Each of the map points has a predicted received signalstrength value. The process 600 determines a projection window 424located at a same vertical level as the second physical level 420 (Block620). Next, the process 600 determines a projected area 444 on thetwo-dimensional radio coverage map 440 by computing a geometricalprojection from the access point 430 through the projection window 424onto the two-dimensional radio coverage map 440 (Block 630). Then, theprocess 600 identifies a plurality of first points located in a firstarea 446 on the two-dimensional radio coverage map 440 (Block 640). Eachof the first points has a predicted received signal strength value. Thefirst area 446 is outside the projected area 444. Next, the process 600reduces the predicted received signal strength value of each of thefirst points by a value equal to the signal attenuation caused by thesecond physical level 420 (Block 650). The process 600 is thenterminated.

FIG. 7 is a flowchart illustrating an embodiment 700 of Block 610 shownin FIG. 6. The process 700 generates a two-dimensional radio coveragemap 440 located between the first physical level 410 and the secondphysical level 420 without taking into account a signal attenuationcaused by the second physical level 420.

Referring to FIG. 7 and FIG. 4, upon START, the process 700 generatescoordinates for each of the map points on a two-dimensional planecorresponding to the two-dimensional radio coverage map 440 (Block 710).Then, the process 700 generates for each of the map points a predictedreceived signal strength value representing a predicted received signalstrength of a signal transmitted by the access point 430 without takinginto account the signal attenuation caused by the second physical level420 (Block 720). The process 700 is then terminated.

Referring to Block 720 of FIG. 7, in one embodiment, the process 700uses an equation corresponding to a simplified path loss model togenerate for each of the map points a predicted received signal strengthvalue.

In one embodiment, the process 700 uses the following equationcorresponding to the simplified path loss model:RSSI=RSSI0−10*pathLossExp*log₁₀(dist2AP)where:

-   -   RSSI=predicted received signal strength value in dBm    -   RSSI₀=received signal strength indicator at a distance of 1        meter from the access point in dBm=(wavelength/(4*π))^2*Ptx

where:

-   -   Wavelength=(speed of light)/(carrier frequency);    -   The wavelength is typically equal to 0.125 meters.    -   Ptx=transmission power;    -   Ptx ranges from −1 dBm to 20 dBm, and is nominally equal to 14        dBm. Any offset from the nominal value of transmission power is        provided as a separate value in assistance information or        broadcast by the access point in 802.11K protocol frames.    -   pathLossExp=path loss exponent;    -   pathLossExp is equal to 2 for free space, 1 to 5 for indoors        environment, and typically is equal to 2.5.    -   dist2AP=distance from the map point being predicted to the        position of the access point.

Referring to Block 620 of FIG. 6 and FIG. 4, in determining a projectionwindow 424 located at a same vertical level as the second physical level420, the process 600 determines a center of the projection window 424and a plurality of points located on a perimeter of the projectionwindow 424 (for example, the four corners of the projection window 424as shown in FIG. 4). The process 600 determines the projection window424 by using information regarding a structural layout of the wirelessenvironment. This information may also include information regardingmaterial types of the plurality of physical levels of the wirelessenvironment. Examples of material types are wood, concrete, metal, etc.

In one embodiment, the projection window 424 located at a same verticallevel as the second physical level 420 is an open space. In other words,the second physical level 420 has an opening. In this embodiment, theprocess 600 determines an open space 424 located at a same verticallevel as the second physical level 420.

In another embodiment, the projection window 424 is not an open spaceand causes a second signal attenuation due to the material type of theprojection window 424. In this embodiment, the process 600 furthercomprises the operation of reducing the predicted received signalstrength value of each of the map points that are located within theprojected area 444 by a value equal to the second signal attenuation.

Referring to Block 640 of FIG. 6 and FIG. 4, in one embodiment, thefirst area 446 on the two-dimensional radio coverage map 440 is adjacentto the projected area 444. In other words, in this embodiment, thetwo-dimensional radio coverage map 440 has two areas that are adjacentto each other, namely, the projected area 444 and the first area 446.

Referring to Block 640 of FIG. 6 and FIG. 4, in another embodiment, thefirst area 446 on the two-dimensional radio coverage map is not adjacentto the projected area 444. In this embodiment, the process 600 furthercomprises the operations of identifying a plurality of transition pointsin a second area 448 on the two-dimensional radio coverage map 440 thatare located between the projected area 444 and the first area 446 andreducing the predicted received signal strength value of each of thetransition points in the second area 448 by a value less than the signalattenuation caused by the second physical level 420. For example, thepredicted received signal strength value of each of the transitionpoints may be reduced by a value equal to half of the signal attenuationcaused by the second physical level 420. The transition points in thesecond area 448 provide a smoother transition from the map pointslocated within the projected area 444 to the map points located in thefirst area 446, in terms of predicted signal strength values. In oneimplementation, the second area 448 forms a 5-meter area around theboundary of the projected area 444.

Before generating the radio coverage map 440, it may be advantageous touse a process to determine approximately whether the access point 430 isradio visible from the first physical level 410. In the wirelessenvironment shown in FIG. 4, the access point 430 is determined to beradio visible from the first physical level 410 if the signalattenuation caused by the second physical level 420 is less than orequal to a threshold.

FIG. 8 is a flowchart illustrating a process 800 of determiningapproximately whether the access point is radio visible from the firstphysical level, in a wireless environment where there are one or morethird physical levels located above the second physical level and wherethe access point is located above the one or more third physical levels.

Upon START, the process 800 computes an aggregate value of signalattenuations caused by the second physical level and the one or morethird physical levels (Block 810). Then, the process 800 compares theaggregate value to a threshold value (Block 820). If the aggregate valueof signal attenuations is less than or equal to the threshold value, theprocess 800 determines that the access point is radio visible from thefirst physical level (Block 830). If the aggregate value of signalattenuations is greater than the threshold value, the process 800determines that the access point is not radio visible from the firstphysical level (Block 840). The process 800 is then terminated. Theprocess 800 may optionally include the operation of checking existenceof an open space extending from the access point 430 to the firstphysical level 410, using information regarding a structural layout ofthe wireless environment.

The process 800 is used first to determine the radio visibility of theaccess point from each of the physical levels of the multi-levelwireless environment. Then, radio coverage maps are generated only forthe physical levels from which the access point is radio visible. Theprocess 800 is particularly beneficial for a mobile station, since themobile station can quickly determine which access points are most likelyto be radio visible from the current coarse position of the mobilestation.

FIG. 9 is a flowchart illustrating a process 900 of generating a radiocoverage map for an access point in a wireless environment according toone embodiment. The wireless environment comprises a plurality ofphysical levels including a first physical level and a second physicallevel.

For clarity of description, FIG. 9 will be described with references tothe example shown in FIG. 5. References made to the example shown inFIG. 5 are only to illustrate one embodiment of the invention where atarget distance 442 is greater than a first distance 552. It isimportant to note that the process 900 is not limited to the illustratedexample of FIG. 5. The process 900 is also applicable for the case wherea two-dimensional radio coverage map is to be placed at a targetdistance that is smaller than the first distance at which a first radiocoverage map is located from the access point.

Referring to FIG. 9, upon START, the process 900 generates a first radiocoverage map 550 comprising a plurality of original points (Block 920).Each of the original points has a first predicted value. The first radiocoverage map is located above the second physical level 420 and at afirst distance 552 from the access point 430. The access point 430 islocated above the second physical level 420. Next, the process 900selects a target distance 442 to place a plurality of map pointscorresponding to the two-dimensional radio coverage map 440 between thefirst physical level 410 and the second physical level 420 and at thetarget distance 442 from the access point 430 (Block 930). Then, theprocess 900 generates coordinates of the map points by magnifying thefirst radio coverage map 550 using the ratio of the target distance 442to the first distance 552 (Block 940). Each of the map pointscorresponds to one of the original points. Then, the process 900computes an offset value representing an attenuation due to the targetdistance 442 being different than the first distance 552 (Block 950).Next, the process 900 generates for each of the map points a predictedreceived signal strength value by adding the offset value to the firstpredicted value of the corresponding one of the original points (Block960). The process 900 is then terminated.

Referring to Block 920 of FIG. 9, the process of Block 920 may comprisethe following operations. First, the process of Block 920 generates theplurality of original points corresponding to a two-dimensional planelocated above the second physical level and at the first distance fromthe access point. Then, the process of Block 920 generates for each ofthe original points on the two-dimensional plane, a first predictedvalue representing a predicted received signal strength of a signaltransmitted by the access point to produce the first radio coverage map550 comprising the original points.

Alternately, the process of Block 920 may also generate a first radiocoverage map by using an existing radio coverage map from a database asthe first radio coverage map 550.

Referring to Block 940 of FIG. 9, to generate coordinates of the mappoints by magnifying the first radio coverage map 550 using a ratio ofthe target distance 442 to the first distance 552, the process 900 usesthe following equations:x _(i) =d _(i) /d ₀ *x ₀;y _(i) =d _(i) /d ₀ *y ₀;where:

-   -   (x_(i), y_(i))=coordinates of one of the map points;    -   (x₀, y₀)=coordinates of a corresponding one of the original        points;    -   d₀=the first distance;    -   d_(i)=the target distance.

It is important to note that, for the case where the target distanced_(i) is smaller than the first distance d₀, the ratio d_(i)/d₀ is lessthan 1 and the coordinates of the map points are generated by magnifyingthe first radio coverage map by a factor of less than 1.

Referring to FIG. 5, the first distance d₀ is the distance 552 from theaccess point 430 to the first radio coverage map 550. As a numericalexample, if the first radio coverage map 550 is placed at a distance 554of 1 meter from the second physical level 420, and the access point 430is located at a distance 552 of 3.5 meters from the second physicallevel 420, then the first distance d₀ is equal to 2.5 meters.

Referring to FIG. 5, the target distance d_(i) is the distance 442 fromthe access point 430 to the two-dimensional radio coverage map 440. As anumerical example, if the two-dimensional radio coverage map 440 isplaced at a distance 412 of 1 meter from the first physical level 410,and the access point 430 is located at a distance 552 of 3.5 meters fromthe second physical level 420, and the distance from the first physicallevel 410 to the second physical level 420 is 4 meters, then the targetdistance d₁ is equal to 6.5 meters.

Referring to Block 950 of FIG. 9, the process 900 computes an offsetvalue representing an attenuation due to the target distance 442 beingdifferent than the first distance 552 using the following equation:RSSIOffset_(i)=10*pathLossExp*log₁₀(d ₀ /d _(i))where:

-   -   RSSIOffset_(i)=the offset value;    -   pathLossExp=path loss exponent;    -   d₀=the first distance;    -   d_(i)=the target distance.

The process 900 may be used as an embodiment of the process 610 shown inFIG. 6 of generating a two-dimensional radio coverage map 440 locatedbetween the first physical level 410 and the second physical level 420without taking into account a signal attenuation caused by the secondphysical level 420.

In the case where simplicity is preferred at the expense of accuracy,the projection window 424 and the projected area 444 are not determined.In such case, the process 900 can be used separately from the process600 as an alternate way of generating a two-dimensional radio coveragemap for the access point 430 as follows. First, the process 900 isperformed as described previously. Then, an additional operation ofreducing the predicted received signal strength value of each of the mappoints by a value equal to the signal attenuation caused by the secondphysical level 420 is performed. In the case where the wirelessenvironment comprises one or more third physical levels located betweenthe first physical level 410 and the second physical level 420, afterthe process 900 is performed, an additional operation of reducing thepredicted received signal strength value of each of the map points by avalue representing an aggregation of signal attenuations caused by thesecond physical level and the one or more third physical levels isperformed.

The methods, sequences and/or algorithms described in connection withthe embodiments disclosed herein can be practiced for any number ofphysical levels in an indoor environment. For example, if there is anaccess point in the space above the fourth physical level of a building,embodiments of the invention can be used to generate radio coverage mapsfor the first, second, third, or fourth physical levels of the buildingand to quickly determine whether the access point is radio visible atany of those physical levels.

FIG. 10 is a diagram illustrating an apparatus 1000 according to oneembodiment. The apparatus 1000 may be included in the location assistantserver 140 of FIG. 1, in the location assistant server 240 of FIG. 2, orin one of the mobile stations 350 of FIG. 3. The apparatus 1000 includesa processor 1010, a chipset 1020, a memory 1030, an interconnect 1040, amass storage medium 1050, and an input/output (I/O) interface 1060. Theapparatus 1000 may include more or less components than the abovecomponents.

The processor 1010 represents a central processing unit of any type ofarchitecture, such as processors using hyper threading, security,network, digital media technologies, single-core processors, multi-coreprocessors, embedded processors, mobile processors, micro-controllers,digital signal processors, superscalar computers, vector processors,single instruction multiple data (SIMD) computers, complex instructionset computers (CISC), reduced instruction set computers (RISC), verylong instruction word (VLIW), or hybrid architecture.

The chipset 1020 provides control and configuration of memory andinput/output devices such as the memory 1030, the mass storage medium1050 and the I/O interface 1060. The chipset 1020 may integrate multiplefunctionalities such as graphics, media, host-to-peripheral businterface, memory control, power management, etc. It may also include anumber of interface and I/O functions such as peripheral componentinterconnect (PCI) bus interface, processor interface, interruptcontroller, direct memory access (DMA) controller, power managementlogic, timer, system management bus (SMBus), universal serial bus (USB)interface, mass storage interface, low pin count (LPC) interface,wireless interconnect, direct media interface (DMI), etc.

The memory 1030 stores code and data. The memory 1030 is typicallyimplemented with dynamic random access memory (DRAM), static randomaccess memory (SRAM), or any other types of memories including thosethat do not need to be refreshed. The memory 1030 may include a radiocoverage map generation module 1035 that performs all or portion of theoperations described above.

The interconnect 1040 provides interface to peripheral devices. Theinterconnect 1040 may be point-to-point or connected to multipledevices. For clarity, not all interconnects are shown. It iscontemplated that the interconnect 1040 may include any interconnect orbus such as Peripheral Component Interconnect (PCI), PCI Express,Universal Serial Bus (USB), Small Computer System Interface (SCSI),serial SCSI, and Direct Media Interface (DMI), etc.

The mass storage medium 1050 includes interfaces to mass storage devicesto store archive information such as code, programs, files, data, andapplications. The mass storage interface may include SCSI, serial SCSI,Advanced Technology Attachment (ATA) (parallel and/or serial),Integrated Drive Electronics (IDE), enhanced IDE, ATA Packet Interface(ATAPI), etc. The mass storage device may include compact disk (CD)read-only memory (ROM), digital video/versatile disc (DVD), floppydrive, hard drive, tape drive, and any other magnetic or optic storagedevices. The mass storage device provides a mechanism to readcomputer-readable media. In one embodiment, the mass storage medium 1050may include flash memory.

The I/O interface 1060 provides interface to I/O devices such as thepanel display or the input entry devices. The I/O interface 1060 mayprovide interface to a touch screen in the graphics display, the keypad,and other communication or imaging devices such as camera, Bluetoothinterface, etc.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments. Likewise, the term “embodiments ofthe invention” does not require that all embodiments of the inventioninclude the discussed feature, advantage or mode of operation. The“computer-readable medium” may include any medium that may store ortransfer information. Examples of the computer-readable medium includean electronic circuit, a semiconductor memory device, a read only memory(ROM), a flash memory, an erasable programmable ROM (EPROM), a floppydiskette, a compact disk (CD) ROM, an optical disk, a hard disk, etc.The computer-readable medium may be embodied in an article ofmanufacture. The computer-readable medium may include information ordata that, when accessed by a processor, cause the processor to performthe operations or actions described above. The computer-readable mediummay also include program code, instruction or instructions embeddedthereon. The program code may include computer-readable code,instruction or instructions to perform the operations or actionsdescribed above. The term “information” or “data” here refers to anytype of information that is encoded for computer-readable purposes.Therefore, it may include program, code, data, file, etc.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of embodiments ofthe invention. As used herein, the singular forms “a”, “an”, and “the”,are intended to include the plural forms as well, unless the contextclearly indicates otherwise. It will be further understood that theterms “comprises”, “comprising”, “includes”, and/or “including”, whenused herein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Further, many embodiments are described in terms of sequences of actionsto be performed by, for example, elements of a computing device. It willbe recognized that various actions described herein can be performed byspecific circuits (e.g., application specific integrated circuits(ASICs)), by program instructions being executed by one or moreprocessors, or by a combination of both. Additionally, these sequencesof actions described herein can be considered to be embodied entirelywithin any form of computer-readable medium having stored therein acorresponding set of computer instructions that, upon execution, wouldcause an associated processor to perform the functionality describedherein. Thus, the various aspects of the invention may be embodied in anumber of different forms, all of which have been contemplated to bewithin the scope of the claimed subject matter. In addition, for each ofthe embodiments described herein, the corresponding form of any suchembodiments may be described herein as, for example, “logic configuredto” perform the described action.

Further, all or part of an embodiment may be implemented by variousmeans depending on applications according to particular features,functions. These means may include hardware, software, or firmware, orany combination thereof. A hardware, software, or firmware element mayhave several modules coupled to one another. A hardware module iscoupled to another module by mechanical, electrical, optical,electromagnetic or any physical connections. A software module iscoupled to another module by a function, procedure, method, subprogram,or subroutine call, a jump, a link, a parameter, variable, and argumentpassing, a function return, etc. A software module is coupled to anothermodule to receive variables, parameters, arguments, pointers, etc.and/or to generate or pass results, updated variables, pointers, etc. Afirmware module is coupled to another module by any combination ofhardware and software coupling methods above. A hardware, software, orfirmware module may be coupled to any one of another hardware, software,or firmware module. A module may also be a software driver or interfaceto interact with the operating system running on the platform. A modulemay also be a hardware driver to configure, set up, initialize, send andreceive data to and from a hardware device. An apparatus may include anycombination of hardware, software, and firmware modules.

Those of skill in the art will appreciate that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Further, those of skill in the art will appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the embodiments disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

The methods, sequences and/or algorithms described in connection withthe embodiments disclosed herein may be embodied directly in hardware,in a software module executed by a processor, or in a combination of thetwo. A software module may reside in RAM memory, flash memory, ROMmemory, EPROM memory, EEPROM memory, registers, hard disk, a removabledisk, a CD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor.

Accordingly, an embodiment of the invention can include acomputer-readable medium embodying a method for efficient generation ofradio coverage map of an access point. Accordingly, the invention is notlimited to illustrated examples and any means for performing thefunctionality described herein are included in embodiments of theinvention.

While the foregoing disclosure shows illustrative embodiments of theinvention, it should be noted that various changes and modificationscould be made herein without departing from the scope of the inventionas defined by the appended claims. The functions, steps and/or actionsof the method claims in accordance with the embodiments of the inventiondescribed herein need not be performed in any particular order.Furthermore, although elements of the invention may be described orclaimed in the singular, the plural is contemplated unless limitation tothe singular is explicitly stated.

What is claimed is:
 1. A method for generating a radio coverage map foran access point in a wireless environment comprising a plurality ofphysical levels including a first physical level and a second physicallevel located above the first physical level, the method comprising:generating, by one of a location assistance server, mobile station, orgeneration module, a two-dimensional radio coverage map located betweenthe first physical level and the second physical level without takinginto account a signal attenuation caused by the second physical level,the access point being located above the second physical level, thetwo-dimensional radio coverage map being located at a target distancefrom the access point and comprising a plurality of map points, each ofthe map points having a predicted received signal strength value;determining a projection window located at a same vertical level as thesecond physical level; determining a projected area on thetwo-dimensional radio coverage map by computing a geometrical projectionfrom the access point through the projection window onto thetwo-dimensional radio coverage map; identifying a plurality of firstpoints in a first area on the two-dimensional radio coverage map, thefirst area being outside the projected area, each of the first pointshaving a predicted received signal strength value; and reducing thepredicted received signal strength value of each of the first points bya value equal to the signal attenuation caused by the second physicallevel.
 2. The method of claim 1 wherein generating the two-dimensionalradio coverage map comprises: generating coordinates for each of the mappoints on a two-dimensional plane corresponding to the two-dimensionalradio coverage map; and generating for each of the map points apredicted received signal strength value representing a predictedreceived signal strength of a signal transmitted by the access pointwithout taking into account the signal attenuation caused by the secondphysical level.
 3. The method of claim 2, wherein generating for each ofthe map points a predicted received signal strength value is performedusing an equation corresponding to a simplified path loss model.
 4. Themethod of claim 1, wherein determining the projection window comprises:determining a center of the projection window and a plurality of pointslocated on a perimeter of the projection window.
 5. The method of claim1, wherein determining the projection window is performed usinginformation regarding a structural layout of the wireless environment.6. The method of claim 5, wherein the information regarding thestructural layout of the wireless environment includes informationregarding material types of the plurality of physical levels.
 7. Themethod of claim 1, wherein determining the projection window comprisesdetermining an open space located at the same vertical level as thesecond physical level.
 8. The method of claim 1, wherein the projectionwindow is not an open space and causes a second signal attenuation, themethod further comprising: reducing the predicted received signalstrength value of each of the map points that are located within theprojected area by a value equal to the second signal attenuation.
 9. Themethod of claim 1, wherein the first area is adjacent to the projectedarea.
 10. The method of claim 1, wherein the first area is not adjacentto the projected area, the method further comprising: identifying aplurality of transition points in a second area on the two-dimensionalradio coverage map that are located between the projected area and thefirst area, each of the transition points having a predicted receivedsignal strength value; and reducing the predicted received signalstrength value of each of the transition points by a value less than thesignal attenuation caused by the second physical level.
 11. The methodof claim 1 further comprising: determining that the access point isradio visible from the first physical level before performing any of thesteps of claim 1; wherein the access point is determined to be radiovisible from the first physical level if the signal attenuation causedby the second physical level is less than or equal to a threshold. 12.The method of claim 1, wherein the wireless environment comprises one ormore third physical levels located above the second physical level andthe access point is located above the one or more third physical levels,the method further comprising: determining that the access point isradio visible from the first physical level, before performing any ofthe operations of the method of claim 1; wherein determining that theaccess point is radio visible comprises: computing an aggregate value ofsignal attenuations caused by the second physical level and the one ormore third physical levels; and determining that the access point isradio visible from the first physical level if the aggregate value ofsignal attenuations is less than or equal to a threshold value.
 13. Themethod of claim 1, wherein generating the two-dimensional radio coveragemap comprises: generating a plurality of original points on atwo-dimensional plane located at a first distance from the access point,between the access point and the second physical level; generating foreach of the original points a first predicted value representing apredicted received signal strength of a signal transmitted by the accesspoint to produce a first radio coverage map comprising the originalpoints; selecting the target distance to place the two-dimensional radiocoverage map at the target distance from the access point; generatingcoordinates of the map points by magnifying the first radio coverage mapusing a ratio of the target distance to the first distance, each of themap points corresponding to one of the original points; computing anoffset value representing an attenuation due to the target distancebeing different than the first distance; and generating for each of themap points a predicted received signal strength value by adding theoffset value to the first predicted value of the corresponding one ofthe original points.
 14. The method of claim 13, wherein generatingcoordinates for each of the map points by magnifying the first radiocoverage map using the ratio of the target distance to the firstdistance is performed in accordance with the following equations:x _(i) =d _(i) /d ₀ *x ₀;y _(i) =d _(i) /d ₀ *y ₀; where: (x_(i), y_(i))=coordinates of one ofthe map points; (x₀, y₀)=coordinates of one of the original points;d₀=the first distance; and d_(i)=the target distance.
 15. The method ofclaim 13, wherein computing the offset value representing theattenuation due to the target distance being different than the firstdistance is performed in accordance with the following equation:RSSIOffset_(i)=10*pathLossExp*log₁₀(d ₀ /d _(i)) where:RSSIOffset_(i)=the offset value; pathLossExp=path loss exponent; d₀=thefirst distance; and d_(i)=the target distance.
 16. An apparatus forgenerating a radio coverage map for an access point in a wirelessenvironment comprising a plurality of physical levels including a firstphysical level and a second physical level located above the firstphysical level, the apparatus comprising: means for generating atwo-dimensional radio coverage map located between the first physicallevel and the second physical level without taking into account a signalattenuation caused by the second physical level, the access point beinglocated above the second physical level, the two-dimensional radiocoverage map being located at a target distance from the access pointand comprising a plurality of map points, each of the map points havinga predicted received signal strength value; means for determining aprojection window located at a same vertical level as the secondphysical level; means for determining a projected area on thetwo-dimensional radio coverage map by computing a geometrical projectionfrom the access point through the projection window onto thetwo-dimensional radio coverage map; means for identifying a plurality offirst points in a first area on the two-dimensional radio coverage map,the first area being outside the projected area, each of the firstpoints having a predicted received signal strength value; and means forreducing the predicted received signal strength value of each of thefirst points by a value equal to the signal attenuation caused by thesecond physical level.
 17. The apparatus of claim 16 wherein the meansfor generating the two-dimensional radio coverage map comprises: meansfor generating coordinates for each of the map points on atwo-dimensional plane corresponding to the two-dimensional radiocoverage map; and means for generating for each of the map points apredicted received signal strength value representing a predictedreceived signal strength of a signal transmitted by the access pointwithout taking into account the signal attenuation caused by the secondphysical level.
 18. The apparatus of claim 17, wherein the means forgenerating for each of the map points a predicted received signalstrength value generates the predicted received signal strength valueusing an equation corresponding to a simplified path loss model.
 19. Theapparatus of claim 16, wherein the means for determining the projectionwindow comprises: means for determining a center of the projectionwindow and a plurality of points located on a perimeter of theprojection window.
 20. The apparatus of claim 16, wherein the means fordetermining the projection window utilizes information regarding astructural layout of the wireless environment.
 21. The apparatus ofclaim 20, wherein the information regarding the structural layout of thewireless environment includes information regarding material types ofthe plurality of physical levels.
 22. The apparatus of claim 16, whereinthe means for determining the projection window comprises the means fordetermining an open space located at the same vertical level as thesecond physical level.
 23. The apparatus of claim 16 wherein theprojection window is not an open space and causes a second signalattenuation, the apparatus further comprising: means for reducing thepredicted received signal strength value of each of the map points thatare located within the projected area by a value equal to the secondsignal attenuation.
 24. The apparatus of claim 16, wherein the firstarea is not adjacent to the projected area, the apparatus furthercomprising: means for identifying a plurality of transition points in asecond area on the two-dimensional radio coverage map that are locatedbetween the projected area and the first area, each of the transitionpoints having a predicted received signal strength value; and means forreducing the predicted received signal strength value of each of thetransition points by a value less than the signal attenuation caused bythe second physical level.
 25. The apparatus of claim 16 furthercomprising: means for determining that the access point is radio visiblefrom the first physical level; wherein the access point is determined tobe radio visible from the first physical level if the signal attenuationcaused by the second physical level is less than or equal to athreshold.
 26. The apparatus of claim 16, wherein the means forgenerating the two-dimensional radio coverage map comprises: means forgenerating a plurality of original points on a two-dimensional planelocated at a first distance from the access point, between the accesspoint and the second physical level; means for generating for each ofthe original points a first predicted value representing a predictedreceived signal strength of a signal transmitted by the access point toproduce a first radio coverage map comprising the original points; meansfor selecting the target distance to place the two-dimensional radiocoverage map at the target distance from the access point; means forgenerating coordinates of the map points by magnifying the first radiocoverage map using a ratio of the target distance to the first distance,each of the map points corresponding to one of the original points;means for computing an offset value representing an attenuation due tothe target distance being different than the first distance; and meansfor generating for each of the map points a predicted received signalstrength value by adding the offset value to the first predicted valueof the corresponding one of the original points.
 27. The apparatus ofclaim 26, wherein the means for generating coordinates of the map pointsby magnifying the first radio coverage map using the ratio of the targetdistance to the first distance generates coordinates of the map pointsin accordance with the following equations:x _(i) =d _(i) /d ₀ *x ₀;y _(i) =d _(i) /d ₀ *y ₀ where: (x_(i), y_(i))=coordinates of one of themap points; (x₀, y₀)=coordinates of one of the original points; d₀=thefirst distance; and d_(i)=the target distance.
 28. The apparatus ofclaim 26, wherein the means for computing the offset value computes theoffset value in accordance with the following equation:RSSIOffset_(i)=10*pathLossExp*log₁₀(d ₀ /d _(i)) where:RSSIOffset_(i)=the offset value; pathLossExp=path loss exponent; d₀=thefirst distance; and d_(i)=the target distance.
 29. An article ofmanufacture comprising a non-transitory computer-readable storage mediumcomprising program code for generating a radio coverage map for anaccess point in a wireless environment comprising a plurality ofphysical levels including a first physical level and a second physicallevel located above the first physical level, the program codecomprising instructions that, when executed by a processor, cause theprocessor to perform operations comprising: generating a two-dimensionalradio coverage map located between the first physical level and thesecond physical level without taking into account a signal attenuationcaused by the second physical level, the access point being locatedabove the second physical level, the two-dimensional radio coverage mapbeing located at a target distance from the access point and comprisinga plurality of map points, each of the map points having a predictedreceived signal strength value; determining a projection window locatedat a same vertical level as the second physical level; determining aprojected area on the two-dimensional radio coverage map by computing ageometrical projection from the access point through the projectionwindow onto the two-dimensional radio coverage map; identifying aplurality of first points in a first area on the two-dimensional radiocoverage map, the first area being outside the projected area, each ofthe first points having a predicted received signal strength value; andreducing the predicted received signal strength value of each of thefirst points by a value equal to the signal attenuation caused by thesecond physical level.
 30. The article of manufacture of claim 29,wherein the instructions causing the processor to perform the operationof generating a two-dimensional radio coverage comprises instructionsthat, when executed by the processor, cause the processor to performoperations comprising: generating coordinates for each of the map pointson a two-dimensional plane corresponding to the two-dimensional radiocoverage map; and generating for each of the map points a predictedreceived signal strength value representing a predicted received signalstrength of a signal transmitted by the access point without taking intoaccount the signal attenuation caused by the second physical level. 31.The article of manufacture of claim 30, wherein the instructions causingthe processor to perform the operation of generating for each of the mappoints a predicted received signal strength value cause the processor toperform the operation using an equation corresponding to a simplifiedpath loss model.
 32. The article of manufacture of claim 29, wherein theinstructions causing the processor to perform the operation ofdetermining the projection window comprises instructions that, whenexecuted by the processor, cause the processor to perform operationscomprising: determining a center of the projection window and aplurality of points located on a perimeter of the projection window. 33.The article of manufacture of claim 29, wherein the instructions causingthe processor to perform the operation of determining the projectionwindow cause the processor to perform the operation using informationregarding a structural layout of the wireless environment.
 34. Thearticle of manufacture of claim 33, wherein the information regardingthe structural layout of the wireless environment includes informationregarding material types of the plurality of physical levels.
 35. Thearticle of manufacture of claim 29, wherein the instructions causing theprocessor to perform the operation of determining the projection windowcause the processor to perform the operation of determining an openspace located at the same vertical level as the second physical level.36. The article of manufacture of claim 29, wherein the projectionwindow is not an open space and causes a second signal attenuation, andwherein the program code further comprising instructions that, whenexecuted by the processor, cause the processor to perform operationscomprising: reducing the predicted received signal strength value ofeach of the map points that are located within the projected area by avalue equal to the second signal attenuation.
 37. The article ofmanufacture of claim 29, wherein the first area is not adjacent to theprojected area, and wherein the program code further comprisinginstructions that, when executed by the processor, cause the processorto perform operations comprising: identifying a plurality of transitionpoints in a second area on the two-dimensional radio coverage map thatare located between the projected area and the first area, each of thetransition points having a predicted received signal strength value; andreducing the predicted received signal strength value of each of thetransition points by a value less than the signal attenuation caused bythe second physical level.
 38. The article of manufacture of claim 29,wherein the program code further comprising instructions that, whenexecuted by the processor, cause the processor to perform operationscomprising: determining that the access point is radio visible from thefirst physical level before performing any of the operations of claim29; wherein the access point is determined to be radio visible from thefirst physical level if the signal attenuation caused by the secondphysical level is less than or equal to a threshold.
 39. The article ofmanufacture of claim 29, wherein the instructions causing the processorto perform the operation of generating a two-dimensional radio coveragecomprises instructions that, when executed by the processor, cause theprocessor to perform operations comprising: generating a plurality oforiginal points on a two-dimensional plane located at a first distancefrom the access point, between the access point and the second physicallevel; generating for each of the original points a first predictedvalue representing a predicted received signal strength of a signaltransmitted by the access point to produce a first radio coverage mapcomprising the original points; selecting the target distance to placethe two-dimensional radio coverage map at the target distance from theaccess point; generating coordinates of the map points by magnifying thefirst radio coverage map using a ratio of the target distance to thefirst distance, each of the map points corresponding to one of theoriginal points; computing an offset value representing an attenuationdue to the target distance being different than the first distance; andgenerating for each of the map points a predicted received signalstrength value by adding the offset value to the first predicted valueof the corresponding one of the original points.
 40. The article ofmanufacture of claim 39, wherein the instructions causing the processorto perform the operation of generating coordinates of the map pointscause the processor to perform the operation in accordance with thefollowing equations:x _(i) =d _(i) /d ₀ *x ₀;y _(i) =d _(i) /d ₀ *y ₀ where: (x_(i), y_(i))=coordinates of one of themap points; (x₀, y₀)=coordinates of one of the original points; d₀=thefirst distance; and d_(i)=the target distance.
 41. The article ofmanufacture of claim 39, wherein the instructions causing the processorto perform the operation of computing the offset value cause theprocessor to perform the operation in accordance with the followingequation:RSSIOffset_(i)=10*pathLossExp*log₁₀(d ₀ /d _(i)) where:RSSIOffset_(i)=the offset value; pathLossExp=path loss exponent; d₀=thefirst distance; and d_(i)=the target distance.
 42. An apparatus forgenerating a radio coverage map for an access point in a wirelessenvironment comprising a plurality of physical levels including a firstphysical level and a second physical level located above the firstphysical level, the apparatus comprising: logic configured to generate atwo-dimensional radio coverage map located between the first physicallevel and the second physical level without taking into account a signalattenuation caused by the second physical level, the access point beinglocated above the second physical level, the two-dimensional radiocoverage map being located at a target distance from the access pointand comprising a plurality of map points, each of the map points havinga predicted received signal strength value; logic configured todetermine a projection window located at a same vertical level as thesecond physical level; logic configured to determine a projected area onthe two-dimensional radio coverage map by computing a geometricalprojection from the access point through the projection window onto thetwo-dimensional radio coverage map; logic configured to identify aplurality of first points in a first area on the two-dimensional radiocoverage map, the first area being outside the projected area, each ofthe first points having a predicted received signal strength value; andlogic configured to predict received signal strength value of each ofthe first points by a value equal to the signal attenuation caused bythe second physical level.
 43. The apparatus of claim 42, furthercomprising: logic configured to generate coordinates for each of the mappoints on a two-dimensional plane corresponding to the two-dimensionalradio coverage map; and logic configured to generate for each of the mappoints a predicted received signal strength value representing apredicted received signal strength of a signal transmitted by the accesspoint without taking into account the signal attenuation caused by thesecond physical level.
 44. The apparatus of claim 43, wherein the logicconfigured to perform the operation of generating for each of the mappoints a predicted received signal strength value is configured toperform the operation using an equation corresponding to a simplifiedpath loss model.
 45. The apparatus of claim 42, further comprising logicconfigured to determine a center of the projection window and aplurality of points located on a perimeter of the projection window. 46.The apparatus of claim 42, wherein the logic configured to perform theoperation of determining the projection window is configured to performthe operation using information regarding a structural layout of thewireless environment.
 47. The apparatus of claim 46, wherein theinformation regarding the structural layout of the wireless environmentincludes information regarding material types of the plurality ofphysical levels.
 48. The apparatus of claim 42, wherein the logicconfigured to perform the operation of determining the projection windowis configured to perform the operation of determining an open spacelocated at the same vertical level as the second physical level.